Fluorine containing polymers have been extensively used to make oil and water repellent coatings on various substrates, primarily on textiles.
Polyaddition polymers as well as polycondensates have been prepared for this purpose. The perfluoroalkyl groups of these polymers impart such low free surface energies to coated surfaces that not only water, but also organic liquids are unable to wet them. Heptane, for instance, with a surface tension of 17 [dynes/cm] will not wet a coating with a surface energy lower than that; surfaces consisting of more or less densely packed perfluoroalkyl groups have free surface energies between 10 and 15 [dynes/cm]. Only very small amounts of fluorine are needed to prepare such surfaces. Therefore, perfluoroalkyl group-containing textile finishes have, despite their greater material cost, replaced to a great extent silicone based water repellents for textile applications.
Silicone based water repellents have, up to the arrival of fluorochemicals, dominated the market of water repellents have, up to the arrival of fluorochemicals, dominated the market of water repellents for textiles. They are still used in applications where only water repellency, no oil repellency, is important and where the exceptionally smooth hand they impart is desired.
Attempts to combine both types of finishes in one application with the goal to get high oil and water repellency together with a soft, smooth hand, have failed, because of the inherent incompatibility of R.sub.f -substituted polymers and polysiloxanes in combination textile finishes. In such combinations of the art, the oil repellency of the fluoropolymer was lost or seriously diminished by combination with silicones.
The combination of siloxane units and fluorine in one molecule for textile applications has been described in U.S. Pat. Nos. 3,331,813 and 3,903,128. In both cases, Si and F are combined in one monomeric unit and fluoroalkyl groups are attached directly to a polysiloxane backbone, covering up in effect the Si atoms. As a result, neither oil repellency nor water repellency is optimized. U.S. Pat. No. 4,098,742 describes polyurethanes which contain at least one segment derived from a perfluoroalkyl-substituted diol and at least one segment derived from a reactive hydrogen containing polysiloxane, synthesized by co-polycondensation with an organic diisocyanate. Polyurethanes of this type, however, are known not to possess the thermal stability required for some textile applications.
It is an object of the present invention to provide thermally stable polysiloxane and fluoroalkyl containing telomers. It is a further object of the present invention to provide oleophobic and hydrophobic coatings of such telomers on substrates particularly glass, ceramic, masonry, wood, paper, metal, leather and preferably textile substrates, to which such coatings impart a high degree of oil repellency, water repellency and soft hand.